Loss of a sense of smell may be an early indication of Alzheimer's disease, research suggests.

Scientists found that changes linked to the most common form of dementia begin in mice in an area of the brain responsible for recognising smells.

The physical symptoms coincided with impaired olfactory, or smell, function. Affected animals had to sniff odors for longer to remember them than healthy mice. They also had problems differentiating between smells.

Noticing similar changes in humans may help in the early detection of Alzheimer's, before the disease has done lasting changes to the brain, say the researchers.

Reduced smelling ability in the genetically-engineered mice was linked to the appearance of amyloid plaques - sticky lumps of protein in the brain that are believed to play a key role in Alzheimer's.